Diabetes is a chronic disorder affecting carbohydrate, fat and protein metabolism in animals.
Type I diabetes mellitus, which comprises approximately 10% of all diabetes cases, was previously referred to as insulin-dependent diabetes mellitus (IDDM) or juvenile onset diabetes. This disease is characterized by a progressive loss of insulin secretory function by beta cells of the pancreas. This characteristic is also shared by non-idiopathic, or “secondary”, diabetes having its origins in pancreatic disease. Type I diabetes mellitus is associated with the following clinical signs or symptoms: persistently elevated plasma glucose concentration or hyperglycemia; polyuria; polydipsia and/or hyperphagia; chronic microvascular complications such as retinopathy, nephropathy and neuropathy; and macrovascular complications such as hyperlipidemia and hypertension which can lead to blindness, end-stage renal disease, limb amputation and myocardial infarction. Therapy for IDDM patients has consistently focused on administration of exogenous insulin, which may be derived from various sources (e.g., human, bovine, porcine insulin). The use of heterologous species material gives rise to formation of anti-insulin antibodies which have activity limiting effects and result in progressive requirements for larger doses in order to achieve desired hypoglycemic effects.
Type II diabetes mellitus (non-insulin-dependent diabetes mellitus or NIDDM) is a metabolic disorder involving the dysregulation of glucose metabolism and impaired insulin sensitivity. Type II diabetes mellitus usually develops in adulthood and is associated with the body's inability to utilize or make sufficient insulin. In addition to the insulin resistance observed in the target tissues, patients suffering from type II diabetes mellitus have a relative insulin deficiency—that is, patients have lower than predicted insulin levels for a given plasma glucose concentration. Type II diabetes mellitus is characterized by the following clinical signs or symptoms: persistently elevated plasma glucose concentration or hyperglycemia; polyuria; polydipsia and/or hyperphagia; chronic microvascular complications such as retinopathy, nephropathy and neuropathy; and macrovascular complications such as hyperlipidemia and hypertension which can lead to blindness, end-stage renal disease, limb amputation and myocardial infarction. Typical treatment of Type II diabetes mellitus focuses on maintaining the blood glucose level as near to normal as possible with lifestyle modification relating to diet and exercise, and when necessary, the treatment with antidiabetic agents, insulin or a combination thereof. NIDDM that cannot be controlled by dietary management is treated with oral antidiabetic agents.
Syndrome X, also termed Insulin Resistance Syndrome (IRS), Metabolic Syndrome, or Metabolic Syndrome X, is recognized in some 2% of diagnostic coronary catheterizations. Often disabling, it presents symptoms or risk factors for the development of Type II diabetes mellitus and cardiovascular disease, including impaired glucose tolerance (IGT), impaired fasting glucose (IFG), hyperinsulinemia, insulin resistance, dyslipidemia (e.g., high triglycerides, low HDL), hypertension and obesity. Although insulin resistance is not always treated in all Syndrome X patients, those who exhibit a prediabetic state (e.g., IGT, IFG), where fasting glucose levels may be higher than normal but not at the diabetes diagnostic criterion, is treated in some countries (e.g., Germany) with metformin to prevent diabetes. The anti-diabetic agents may be combined with pharmacological agents for the treatment of the concomitant co-morbidities (e.g., antihypertensives for hypertension, hypolipidemic agents for lipidemia).
Hyperglycemia is one common characteristic of these diabetic disorders. Treatments of hyperglycemia are focused on excretion of excessive glucose directly into urine, which involves sodium-glucose cotransporters (SGLTs), primarily found in the chorionic membrane of the intestine and kidney. In particular, renal reabsorption of glucose is mediated by SGLT1 and SGLT2 (MARSENIC, O., “Glucose Control by the Kidney: An Emerging Target in Diabetes”, AM. J. Kidney Dis., 2009 May, pp 875-883, Vol. 53(5); WRIGHT, E. M., et al., “Biology of Human Sodium Glucose Transporters”, Physiol. Rev., 2011 April, pp 733-794, Vol. 91(2)). SGLT1, a high-affinity low-capacity transporter with a Na+:glucose transport ratio of 2:1, is present in intestinal and renal epithelial cells (LEE, W. S., et al., “The High Affinity Na+/Glucose Cotransporter. Re-evaluation of Function and Distribution of Expression”, J. Biol. Chem., 1994 Apr. 22, pp 12032-12039, Vol. 269(16)). On the other hand, SGLT2, also known as SAAT1, a low-affinity high-capacity transporter with a Na+:glucose transport ratio of 1:1, is found in the epithelium of the kidney (YOU, G., et al., “Molecular Characteristic of Na(+)-coupled Glucose Transporters in Adult and Embryonic Rat Kidney”, J. Biol. Chem., 1995 Dec. 8, pp 29365-29371, Vol. 270(49); CHEN, J., et al., “Quantitative PCR Tissue Expression Profiling of the Human SGLT2 Gene and Related Family Members”, Diabetes Ther., 2010 December, pp 57-92, Vol. 1(2)). In addition, glucose absorption in the intestine is primarily mediated by SGLT1 and SGLT2. Thus, inhibition of SGLT1 and SGLT2 reduces plasma glucose through suppression of glucose reabsorption in the kidney, which was demonstrated in rodent models of IDDM and NIDDM by increasing the excretion of glucose in urine and lowering blood glucose levels.
Non-alcoholic fatty liver disease (NAFLD) is one cause of a fatty liver, occurring when fat is deposited (steatosis) in the liver. NAFLD is considered to cover a spectrum of disease activity. This spectrum begins as fatty accumulation in the liver (hepatic steatosis). A liver can remain fatty without disturbing liver function, but by varying mechanisms and possible insults to the liver may also progress to become NASH, a state in which steatosis is combined with inflammation and fibrosis. Non-alcoholic steatohepatitis (NASH) is a progressive, severe form of NAFLD. Over a 10-year period, up to 20% of patients with NASH will develop cirrhosis of the liver, and 10% will suffer death related to liver disease. The exact cause of NAFLD is still unknown, however, both obesity and insulin resistance are thought to play a strong role in the disease process. The exact reasons and mechanisms by which the disease progresses from one stage to the next are not known.
NAFLD has been linked to insulin resistance (IR) and the metabolic syndrome (MS). As the renin-angiotensin system (RAS) plays a central role in insulin resistance, and subsequently in NAFLD and NASH, an attempt to block the deleterious effects of RAS overexpression has been proposed a target for treatment. While many potential therapies tested in NASH target only the consequences of this condition, or try to “get rid” of excessive fat, angiotensin receptor blockers (ARBs) may act as a tool for correction of the various imbalances that act in harmony in NASH/NAFLD. Indeed, by inhibiting RAS the intracellular insulin signaling pathway may be improved, resulting in better control of adipose tissue proliferation and adipokine production, as well as more balanced local and systemic levels of various cytokines. At the same time, by controlling the local RAS in the liver fibrosis may be prevented and the cycle that links steatosis to necroinflammation slowed down. (GEORGESCU, E. F., in Advances in Therapy, 2008, pp 1141-1174, Vol. 25, Issue 11)
SCAFOGLIO, C., et al., in “Functional expression of sodium-glucose transporters in cancer”, PNAS, 2015, pp E41111-E4119, Vol 112(3), describe the role of sodium-dependent glucose transporters (SGLTs) in pancreatic and prostate adenocarcinomas, and their role in cancer cell survival. SGLT2 was found to be functionally expressed in pancreatic and prostate adenocarcinomas and further found to block glucose uptake and reduce tumor growth and survival in a xenograft model of pancreatic cancer, suggesting that SGLT2 inhibitors could be useful in treating certain types of cancers.
There remains a need for SGLT inhibitor compounds that have pharmacokinetic and pharmacodynamic properties suitable for use as human pharmaceuticals.